The state of mind one gets after smoking an incredibly large amount of marijuana, whether in bong, joint, or bowl form.
Usually, it is a very cerebral and intense high, making one do things they normally would not do when sober.

"Fuck, man! I am so shamaaannneeeddddddd"

"Dude I got so shamaned last night, I started a World of Warcraft account for my sister"

"I pissed all over myself after I got home from the Lord of the Rings marathon last night, man... I was so shamaned"